A substrate treating apparatus includes a holding rotator, nozzles, and a pump apparatus. See, for example, Japanese Patent No. 5451515. The holding rotator holds a substrate in a substantially horizontal attitude, and rotates the held substrate. The nozzles each dispense a processing liquid to the substrate held with the holding rotator. The pump apparatus supplies the processing liquid to the nozzles.
As illustrated in FIG. 1, the pump apparatus 100 include an upstream pump 101, a downstream pump 102, and a filter 104 inserted into a processing liquid pipe 103. The upstream pump 101 and the downstream pump 102 are disposed in parallel in a horizontal direction. See, for example, Japanese Patent No. 5366555 and 5079516, and U.S. Pat. No. 6,251,293. Here, FIG. 1 indicates an upward/downward (vertical) direction with an arrow AR.